Business track 🧭 · four sessions, no code
For marketing, BD and leaders who ask for a market size and are judged on the bet it supports. The decision before the number, the category before the size, the questions to ask of any sizing slide, the one-page brief that splits the evidence from the bet, and an evidence gate before anyone believes a share figure.
What a market size is for
The decision a size informs, TAM, SAM and SOM and why TAM is the least useful of the three, and why the category is chosen before the size.
🔍Business session 2Reading a sizing deck
The hero assumption that inflates a size tenfold, vanity TAMs, "1% of a huge market", analyst-report numbers with no method, and five questions for any sizing slide.
🤝Business session 3Who owns which half
Data owns the evidence, marketing and BD own the bet. The one-page sizing brief: question, decision, owner, category, method, range, and the assumption that would change the call.
🪜Business session 4From size to plan
Realistic penetration and ramp, base rates as a discipline, and an evidence gate in your own numbers before anyone believes the share figure.
Analyst track 🧮 · six sessions, hands-on in the browser
For the data analysts and data scientists who build the size. Every widget computes in your browser on real rows from the Statistics Bureau of Japan: 2020 Census households and the Family Income and Expenditure Survey's tea spend. The bench puts top-down and bottom-up side by side and lets you break it twice.
Top-down: from public statistics to your segment
Households times spend per household times your shares, on Japan's own rows. Who the survey asked, what its items mean, and one city's rate applied to a country.
🧾Analyst session 2Bottom-up: customers, price and frequency
Buyers times spend per order times orders a year, from your own data. Where each input comes from, and the range each one deserves.
🧭Analyst session 3Sizing by analogy and proxy
Comparable markets, adjacent categories, search volume, job postings and import statistics, each with its failure mode; the office tea question no table measures.
🌪️Analyst session 4Ranges, not points
Every assumption gets a low and a high, ranges as corners, and a tornado that shows which assumption moves the answer most.
📈Analyst session 5Share realism and the collision test
Adoption curves as a shape, base rates for new entrants, distribution ceilings, and the test that adds up every entrant's planned share of the same market.
📐Analyst session 6 · bench nightThe triangulation bench
Top-down meets bottom-up: the gap, the overlap, the assumption that explains most of it, a category toggle, the hero assumption and the analyst number with no method.
Your passport 🎫
Clear all three quiz questions in a session and it gets stamped. Ten stamps means you can tie a size to a decision, read a sizing deck for its hero assumption, build a size two ways on real rows and say what the gap between them means. Stamps live in this browser only.
What this is not, so you land in the right place 🧭
| If your question is | Go here instead |
|---|---|
| Whose job is market research, and how does data take asks from marketing and BD? | Marketing Analytics ↗ |
| I am a marketer: how do I position, plan and budget? | Marketing ↗ |
| Which strategy framework fits this choice? | Strategic Thinking ↗ |
| How do price and elasticity change demand? | Economics ↗ |
| How do I forecast a market's growth over time? | Timeseries Forecasting ↗ |
| Someone needs a market size for a decision, and I either ask for it or build it. | you are in the right place |
Market sizing as evidence for a decision. Kettle & Co is constructed; the households and tea spend are read from the Statistics Bureau of Japan at source; contested claims, such as analyst-firm market sizes and "the right method", are taught as contested.
Choose your path 🗺️
Three doors into the same conviction: a market size is evidence for a decision, built two ways and stated as a range.
What is honest here 🧾
The running company is constructed and says so on every page. The households and the tea spend are real and named with their table and year. Where a claim is contested, the page teaches both sides.
| Claim | Status |
|---|---|
| Kettle & Co, its people, shares, pilot numbers, plans and the analyst figure | Constructed, and labelled each time |
| Japan's households (2020 Census) and tea spend per household (Family Income and Expenditure Survey, 2023-2025 average) | Read at source from the Statistics Bureau of Japan |
| Every number on the widgets and the bench | Computed in your browser from those rows and the constructed inputs; a Python reference prints the same numbers |
| The big market delusion | Read at source in Aswath Damodaran's own blog posts, and cited in that form |
| Positioning order, scaling readiness, diffusion curves | Reported from the authors' books and papers, paraphrased, never quoted |
| Analyst-firm market sizes; top-down against bottom-up as "the right" method | Contested, and taught as contested |
The knowledge map 🧠
Both tracks at a glance - hover a session to spotlight its concepts, click any node to jump in.